The major difference between several of the higher ranks is that you get the "higher" rank if you have certain badges. Whichever rank you get, each pair only gives you one unlock.
It is also worth noting that the upper ranks are not progressive. You will only earn one rank per point bracket. If you make it to Master Sergeant without the awards, you will not be promoted to First upon earning the missing awards.
Private Requirements:

  • Notes: First Rank, No Reqs

Private First Class Requirements:

  • Score: 150

Lance Corporal Requirements:

  • Rank: Private First Class
  • Score: 500
  • Unlock Available

Corporal Requirements:

  • Rank: Lance Corporal
  • Score: 800
  • Unlock Available

Sergeant Requirements:

  • Rank: Corporal
  • Score: 2,500
  • Unlock Available

Staff Sergeant Requirements:

  • Rank: Sergeant
  • Score: 5,000
  • Unlock Available

Gunnery Sergeant Requirements:

  • Rank: Staff Sergeant
  • Score: 8,000
  • Unlock Available

Master Sergeant Requirements:

  • Rank: Gunnery Sergeant
  • Score: 20,000
  • Unlock Available

First Sergeant Requirements:

  • Rank: Gunnery Sergeant
  • Score: 20,000
  • Awards: Basic Knife Combat Badge, Basic Pistol Combat Badge, Basic Assault Combat Badge, Basic Anti-tank Combat Badge, Basic Sniper Combat Badge, Basic Spec Ops Combat Badge, Basic Support Combat Badge, Basic Engineer Combat Badge, Basic Medic Combat Badge

Master Gunnery Sergeant Requirements:

  • Rank: Master Sergeant
  • Score: 50,000
  • Unlock Available

Sergeant Major Requirements:

  • Rank: Master Sergeant
  • Score: 50,000
  • Awards: Basic Armor Badge, Basic Transport Badge, Basic Helicopter Badge, Basic Aviator Badge, Basic Air Defense Badge, Basic Ground Defense Badge

Sergeant Major of the Corps Requirements:

  • Rank: Master Sergeant
  • Notes: This rank is only awarded to one player at a time. It can not be earned in game via points/awards.

2nd Lieutenant Requirements:

  • Rank: Master Gunnery Sergeant
  • Score: 60,000

1st Lieutenant Requirements:

  • Rank: 2nd Lieutenant
  • Score: 75,000

Captain Requirements:

  • Rank: 1st Lieutenant
  • Score: 90,000

Major Requirements:

  • Rank: Captain
  • Score: 115,000

Lieutenant Colonel Requirements:

  • Rank: Major
  • Score: 125,000

Colonel Requirements:

  • Rank: Lieutenant Colonel
  • Score: 150,000

Brigadier General Requirements:

  • Rank: Colonel
  • Score: 180,000
  • Awards: Veteran Armor Badge, Veteran Transport Badge, Veteran Helicopter Badge, Veteran Aviator Badge, Veteran Air Defense Badge, Veteran Ground Defense Badge
  • Notes: Requires 1080 hours playtime

Major General Requirements:

  • Rank: Brigadier General
  • Score: 180,000
  • Awards: Veteran Knife Combat Badge, Veteran Pistol Combat Badge, Veteran Assault Combat Badge, Veteran Anti-tank Combat Badge, Veteran Sniper Combat Badge, Veteran Spec Ops Combat Badge, Veteran Support Combat Badge, Veteran Engineer Combat Badge, Veteran Medic Combat Badge
  • Notes: Requires 1250 hours playtime

Lieutenant General Requirements:

  • Rank: Major General
  • Score: 200,000
  • Notes: Requires 1440 hours playtime

General Requirements:

  • Rank: Lieutenant General
  • Score: 200,000
  • Notes: Highest rank of the month